"Counts as Class X for Feat Type Y" ability

[shatterjack]

I'm trying my hand at implementing the Stalker from Path of War, and I'm currently working on Critical Training from Stalker Arts. In addition to increasing Deadly Strike dice by one (which was easy enough), it also allows Stalker levels to count as Fighter levels for the purposes of qualifying for critical feats.

How do I go about this in the scripts for the ability? I'm hoping the answer isn't "edit every single critical feat in the game and add a check for this ability", since I'd rather keep things contained in my own files if possible. I feel like there should be an existing Class Special or Custom Ability that I could use as a base, but none come to mind.